The invention relates to a method and an apparatus for energizing ultrasonic transducers which are used in impulse echo technology, in particular, in the examination of the human body, whereby, in order to energize for the purpose of transmitting an ultrasonic pulse, there is fed to the ultrasonic transducer, respectively, an electric high frequency pulse of fixed duration and amplitude.
Ultrasonic transducers of the cited type are utilized particularly in the so-called B-scan technique, wherein an examination subject, for example, the human body, is scanned in a linear fashion with ultrasonic pulses and wherein the echo signals received from the subject are correspondingly recorded in a linear fashion into an areal echo-visual image on a recording apparatus (e.g. a cathode ray oscilloscope). However, the transducers can likewise be those of the A-scan technique or another scan technique. In the case of the B-scan technique, the transducer can be a so-called rotational transducer with a paraboloid reflector. It can likewise also be a transducer capable of linear displacement, or a pivotal transducer for e.g. sector-scan. In this category, finally, are also included transducers of a compound-scan system, and, in particular, also so-called ultrasonic arrays, wherein a plurality of adjacently arranged ultrasonic transducers can be energized in chronological sequence.
In all these applied instances, the electric excitation of the ultrasonic transducers (in particular, piezo-electric transducers) proceeds, in the normal instance, by means of a short pulse of very high amplitude (several 100 V). This type of excitation is the most effective method with regard to use and electronic outlay as long as the voltage amplitudes are not subject to any major restriction. However, such restrictions occur automatically if electronic switches are to be utilized for the purpose of controlling ultrasonic transducers, which switches, due to spatial and functional dimensioning, are restricted in the maximum switching (or interruption) voltage. A particular technique field is here the array technology wherein one or more electronic switches must be allocated to each individual transducer. For reasons of cost and also for reasons of improved spatial utilization, there is an interest in the introduction of integrated switches. The maximum switching (or interruption) voltage of such switches, however, is generally restricted to approximately 30 to 40 V. The introduction of switches with such a limited switching (or interruption) voltage thus leads to a considerable reduction in the voltage amplitude to be energized; in the case of application (for example, the human body), this signifies a considerable loss of penetration depth for the ultrasonic transmission pulses.